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// TODO: Use `adt_const_params` once stabilized to make a `Residue` generic around a modulus rather than having to implement a ZST + trait
#[macro_export]
/// Implements a modulus with the given name, type, and value, in that specific order. Please `use crypto_bigint::traits::Encoding` to make this work.
/// For example, `impl_modulus!(MyModulus, U256, "73eda753299d7d483339d80809a1d80553bda402fffe5bfeffffffff00000001");` implements a 256-bit modulus named `MyModulus`.
/// The modulus _must_ be odd, or this will panic.
macro_rules! impl_modulus {
($name:ident, $uint_type:ty, $value:expr) => {
#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
pub struct $name {}
impl<const DLIMBS: usize>
$crate::modular::constant_mod::ResidueParams<{ <$uint_type>::LIMBS }> for $name
where
$uint_type: $crate::ConcatMixed<MixedOutput = $crate::Uint<DLIMBS>>,
{
const LIMBS: usize = <$uint_type>::LIMBS;
const MODULUS: $uint_type = {
let res = <$uint_type>::from_be_hex($value);
// Check that the modulus is odd
if res.as_limbs()[0].0 & 1 == 0 {
panic!("modulus must be odd");
}
res
};
const R: $uint_type = $crate::Uint::MAX
.const_rem(&Self::MODULUS)
.0
.wrapping_add(&$crate::Uint::ONE);
const R2: $uint_type =
$crate::Uint::const_rem_wide(Self::R.square_wide(), &Self::MODULUS).0;
const MOD_NEG_INV: $crate::Limb = $crate::Limb(
$crate::Word::MIN.wrapping_sub(
Self::MODULUS
.inv_mod2k_vartime($crate::Word::BITS as usize)
.as_limbs()[0]
.0,
),
);
const R3: $uint_type = $crate::modular::montgomery_reduction(
&Self::R2.square_wide(),
&Self::MODULUS,
Self::MOD_NEG_INV,
);
}
};
}
#[macro_export]
/// Creates a `Residue` with the given value for a specific modulus.
/// For example, `residue!(U256::from(105u64), MyModulus);` creates a `Residue` for 105 mod `MyModulus`.
/// The modulus _must_ be odd, or this will panic.
macro_rules! const_residue {
($variable:ident, $modulus:ident) => {
$crate::modular::constant_mod::Residue::<$modulus, { $modulus::LIMBS }>::new(&$variable)
};
}